Research Article www.acsami.org
Strong Piezoelectricity in (1 − x)(K0.4Na0.6)(Nb0.96Sb0.04)O3‑xBi0.5K0.5Zr1−ySnyO3 Lead-Free Binary System: Identification and Role of Multiphase Coexistence Ting Zheng, Jiagang Wu,* Dingquan Xiao, and Jianguo Zhu Department of Materials Science, Sichuan University, Chengdu 610064, P. R.China
Xiangjian Wang, Lipeng Xin, and Xiaojie Lou Multi-disciplinary Materials Research Center, Frontier Institute of Science and Technology, and State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049, P. R. China S Supporting Information *
ABSTRACT: Here we report a strong piezoelectric activity in (1 − x)(K0.4Na0.6)(Nb0.96Sb0.04)O3-xBi0.5K0.5Zr1−ySnyO3 lead-free ceramics by designing different phase boundaries. The phase boundaries concerning rhombohedral-orthorhombic-tetragonal (R-O-T) and rhombohedral-tetragonal (R-T) multiphase coexistence were attained by changing BKZS and Sn contents and then were identified by the X-ray diffraction patterns as well as temperature-dependent permittivity and ν1 Raman modes associated with BO6 perovskite octahedron. A high strain (strain = 0.21−0.28% and d33* = 707−880 pm/V) and a strong piezoelectric coefficient (d33 = 415−460 pC/ N) were shown in the ceramics located at the multiphase coexistence region. The reported results of this work are superior to that (d33* ∼ 570 pm/V and d33 ∼ 416 pC/N) of the textured (K,Na,Li)(Nb,Ta,Sb)O3 ceramics [Nature 2004, 432, 84]. We believe that the material system of this work will become one of the most promising candidates for piezoelectric actuators. KEYWORDS: potassium−sodium niobate, multiphase coexistence, strong piezoelectric activity, physical mechanism
■
V).10 Since then, (K,Na)NbO3 (KNN) ceramics have been considered as promising candidates to replace the lead-based ones.11−19 Nevertheless, a relatively low strain (0.1−0.2%) was observed in KNN-based ceramics prepared by conventional solid-state methods.11−14 Therefore, it has become an urgent task to search for a kind of KNN-based ceramics with balanced developments of d33 and d33*. In the past several years, there have been some reports on the strain investigations in (Bi0.5Na0.5)TiO3 and BaTiO3-based ceramics, and the Sn4+ substitutions for Ti4+ site can effectively enhance their strain behavior.2−9 For example, a relatively high d33* value of 585 pm/V can be observed when the 5% mol SnO2 was used to modify Bi0.5(Na0.82K0.18)0.5TiO3.4 Furthermore, the Sn can promote piezoelectric and strain behavior of BaTiO3-based ceramics.5 As a result, it was highly expected that the doping with Sn4+ may improve the strain behavior of KNNbased ceramics. To our knowledge, there were few reports on the strain investigations on the Sn-doped KNN ceramics together with a strong piezoelectric activity. In addition, the
INTRODUCTION Lead-based ceramics possess an excellent piezoelectric constant (d33) and high electric field-induced strain1 and are currently applied in many electronic devices. However, most researchers have recently given considerable attention to lead-free piezoceramics because the hazardous Pb element will be gradually prohibited in electronic devices.2−40 Due to the importance of high strain in piezoelectric actuators, related research has recently become very active.2−14,30−35 Previously, it was reported that a high strain could be well developed in the Bi1/2Na1/2TiO3 (BNT)-based ceramics,2−4 but the poor d33 values (300 pC/N can be observed for 0.03 ≤ x ≤ 0.045 even if Ta almost approaches TC. That is, even if the ceramics exhibit a slightly poor thermal stability of d33, a larger d33 can effectively solve this issue. In addition, the addition of optimum Sn content (y ≤ 0.2) can promote the thermal stability of d33 (see Figure 14c,d), while their stability decreases gradually with further increasing y.
■
CONCLUSION In this work, our objective is to promote both piezoelectric properties and strain of the KNN-based ceramics by constructing multiphase coexistence and then identify the 5934
DOI: 10.1021/acsami.5b00151 ACS Appl. Mater. Interfaces 2015, 7, 5927−5937
Research Article
ACS Applied Materials & Interfaces Table 1. Relationship between Phase Boundary and Piezoelectricity in Piezoceramics material system Pb-based Bi-layered BaTiO3 -based BNT-based KNN-based
phase boundary
compositions PZT4 (Na0.78K0.22)0.5TiO3-xBi(Mg0.5Ti0.5)O3 BaTiO3−(0.4CaTiO3−0.6BaSnO3) 0.94(1 − x)Bi0.5Na0.5TiO3−0.06BaTiO3 −xK0.5Na0.5NbO3 (K0.44Na0.52Li0.04)(Nb0.84Ta0.10Sb0.06)O3 K0.5−x/2Na0.5−x/2LixNbO3 K0.5−x/2Na0.5−x/2LixNb1−yTayO3 0.92(Na0.535K0.48)NbO3−0.08LiNbO3 (K1−xNax)0.92Li0.08NbO3 K0.5Na0.5Nb0.7Ta0.3O3 (Na0.52K0.48)(Nb1‑xSbx)O3 x = 0.12 (1 − x)(K0.4Na0.6)(Nb0.96Sb0.04)O3-xBi0.5K0.5Zr1‑ySnyO3 (x = 0.03, y = 0.1) (1 − x)(K0.4Na0.6)(Nb0.96Sb0.04)O3-xBi0.5K0.5Zr1‑ySnyO3 (x = 0.04, y = 0.1)
R-T T R-O-T O-T O-T O-T O-T R-O-T R-O-T R-T
d33 pC/N strain %
d33* pm/V
TC (°C)
ref
410 570
